2 x 500ml emptied cold drink bottles
Take the wrappers off of your plastic bottles and use a Sharpie to draw 5cm x 10cm cut-out lines. Your measurements don’t have to be exact, in fact, they might vary depending on the circumference of your bottles. Hold a Barbie up next to your bottles to get a better idea. They should fit snuggly to keep them sitting up right and prevent them from falling out.
Use a utility knife and/or scissors to cut out your boat openings. A utility knife makes it easier to get your cut started, but sharp scissors will work, too.
Tape the bottles together at the biggest part, as well as a thin strip around the back. Also, tape the potentially sharp edges where you made your cut-outs.
Now, get your Barbies and take them for a spin in their new awesome Barbie boat.